Summary

Growth hormone (GH) and lactic acid levels were measured in five normal males before, during and after two different types of exercise of nearly equal total duration and work expenditure. Exercise I (aerobic) consisted of continuous cycling at 100 W for 20 min. Exercise II (anaerobic) was intermittent cycling for one minute at 285 W followed by two minutes of rest, this cycle being repeated seven times. Significant differences (P<0.01) were observed in lactic acid levels at the end of exercise protocols (20 min) between the aerobic (I) and anaerobic (II) exercises (1.96±0.33 mM·l−1 vs 9.22±0.41 mM·l−1, respectively). GH levels were higher in anaerobic exercise (II) than in aerobic (I) at the end of the exercise (20 min) (2.65±0.95 Μg·l−1 vs 0.8±0.4 Μg·l−1;P<0.10) and into the recovery period (30 min) (7.25±6.20 Μg·l−1 vs 2.5±2.9 Μg·l−1;P<0.05, respectively).